Author Paul French dived into historical archives about the case to write his 2012 bestseller, Midnight in Peking.

His theory is based on a suspect list compiled by the victim's adoptive father, retired British consular official Edward Werner.

French believes the prime suspects are three Western men — a marine, an American dentist and an Italian doctor.

As the theory goes, the men, who hunted together in the woods nearby, may have lured Pamela to a brothel — in the area known as the Badlands — and then killed her.

But does the theory stack up?

Murder intrigues veteran policeman

Retired British policeman Graeme Sheppard doesn't think so.

Sheppard, a veteran of 30 years on the force, became intrigued with the brutal cold case after reading French's book.

Though he doesn't usually read crime novels, a family connection — his wife's grandfather Nicholas Fitzmaurice was a consul in Peking and had been coroner in the case — prompted him to pick up the book.

"It was a foul sadist [sic] crime, committed in all probability at one of those sexual orgies which are such a crying disgrace to the foreign community in Peking," Werner wrote.

But no-one was ever charged, partly due to the outbreak of war between China and Japan.

Decades on, Sheppard decided to re-examine the case for himself.

The 'strongest suspect'

He reviewed Werner's letters of complaint to the Foreign Office about the investigation, and formed a new theory, which he outlined in his own book A Death in Peking: Who Killed Pamela Werner?

"Pamela's father came up with his own list of suspects, as to who he thought had committed the crime," says Sheppard.

"In my opinion he is a stronger candidate than his own list. He had a history of violence, he was very controlling, very insecure.

"He knew Pamela's movements that day, he knew her route home, he knew she was growing up and had boyfriends, he may have disapproved of whatever activities she was up to with boyfriends and he had an explosive temper.

"He also turned up at the crime scene the following morning, as offenders for some reason often do."

Having said that, though, Sheppard doesn't believe Werner killed his only child.

Rather, he believes a former boyfriend of Pamela's, a Chinese student by the name of Han Shou-ch'ing, is the "strongest suspect".

That belief was also shared by the top British cop who oversaw the initial investigation in the 1930s.

"The word of the man overseeing the case … carries a great deal of weight," Sheppard says.

Sheppard believes the removal of Pamela's heart could been seen as an act of revenge.

He also claims Pamela's father disapproved of the relationship and had admitted to once breaking the student's nose.

"The crime scene just around the corner from the home, on the route home from the ice rink, supports the idea of a lone offender who had the motive of resentment, lust, rejection and obsession, and revenge of her father," he says.

"And of all the suspects … he is the only one who has disappeared, who there is no trace of, who is untraceable for the police at the time."

'It's like a 100-year grudge match'

French had defended his book and questions Sheppard's impartiality, given the family connection.